Frontotemporal dementia is difficult to differentiate from other forms of dementia due to their similarities in symptoms. That being said, the age of onset is generally younger than in other types of dementia. In frontotemporal dementia, the frontal and temporal lobes of the brain are affected, which causes a disruption to memory, speech, movement and personality. The aim of this article is to inform you on how frontotemporal dementia is investigated and diagnosed. 

What is frontotemporal dementia?

Frontotemporal dementia is a neurological condition in which there is deterioration in the functioning of the nerve cells in the frontal and temporal lobes of the brain. As mentioned above, it is the most common form of dementia amongst people under the age of 65 and is the third most common form of dementia overall.¹

There are different subtypes of frontotemporal dementia. Presentation of symptoms in each variant is dependent on the exact area of neuronal degeneration.² The different variants include:

• Behaviour variant: This is the most common variant of frontotemporal dementia and presents with changes in personality and behaviour. There is often a loss of inhibition, increase in non-conducive abstract thinking and loss of emotional reactivity. Patients may also exhibit changes in eating patterns and loss of empathy. Memory will often stay intact until the later stages of the disease
• Semantic variant: Patients will have trouble with speech and language, such as having trouble finding the right word or experiencing loss of vocabulary. In some cases, it may be that their speech is comprehensible but, the content of speech does not make sense. It could be the case where their speech is incomprehensible. They may also have trouble recognising unfamiliar faces or objects. As with the behavioural variant, memory is often affected in the later stages of the disease
• Non-fluent variant primary progressive aphasia: Patients will experience the same as the semantic variant in addition to having trouble understanding complex sentences and naming even familiar objects

In all of the above forms of frontotemporal dementia, the patient’s quality of life and ability to live a normal daily life is largely diminished.

What is the differential diagnosis for frontotemporal dementia?

Upon initial presentation of symptoms, frontotemporal dementia can easily be mistaken for a stroke. It can also be mistaken for other psychiatric disorders, such as the following:

• Alzheimer disease
• Vascular dementia
• Lewy body dementia
• Parkinsonism
• Supranuclear palsy
• Alcoholism
• Bipolar disorders
• Schizophrenia
• Borderline personality disorder
• Obsessive-compulsive disorder

In order to differentiate frontotemporal dementia from these conditions, it is important to establish a thorough history and complete the necessary diagnostic tests.

What is the diagnostic criteria for the different types of frontotemporal dementia? 

There are different diagnostic criteria for the different types of frontotemporal dementia.³

Behavioural variant frontotemporal dementia definitive diagnostic criteria:

• Patient shows the symptoms listed for behavioural variant frontotemporal dementia as stated in the above section
• AND/OR patient experiences functional decline, and their imaging is consistent with behavioural variant frontotemporal dementia
• AND/OR their cells show evidence of frontotemporal dementia during post-mortem investigation, and/or there is presence of a known disease-causing organism with a mutation

Semantic variant frontotemporal dementia definitive diagnostic criteria:

• The loss of semantic knowledge (knowledge gained essentially through experiencing life) leads to a decrease in single-word comprehension and ability to name objects
• At least three of the following:
  • Speech repetition 
  • A reduction in the ability to form words (can lead to problems with grammar)
  • Problems with reading and writing
  • Problems recognising objects that they wouldn’t come across in their day-to-day life

Non-fluent variant primary progressive aphasia definitive diagnostic criteria:

• Speech with inconsistencies with grammar or the ability to speak at all with effortful pauses in speech and errors in forming sounds when speaking 
• At least two of the following:
  • Trouble understanding complex sentences
  • Trouble understanding singular words here and there
  • Trouble recognising even everyday objects here and there

What are the diagnostic tests and imaging utilised in diagnosing frontotemporal dementia?²

The very first diagnostic tools used should be the use of neurocognitive interviews, especially in primary care settings such as a GP. The most common exam used is the Mini-Mental State Examination, which is a questionnaire that assesses dementia in general by testing the patient’s memory, orientation in time and space, attention to detail, cognition, language, and executive functions. Other neurocognitive tests that can be used include:

• Informant questionnaire for cognitive disorders in the elderly
• Montreal cognitive assessment
• Functional cognitive assessment

Laboratory tests can be conducted on blood and cerebrospinal fluid taken from the patient to test for the presence of specific proteins and other biomarkers that indicate frontotemporal dementia.

Radiological imaging in the form of an MRI scan or a CT scan can show evidence of shrinking in the frontal and/or temporal lobes in cases of frontotemporal dementia. Imaging can also be used to rule out other neurological conditions. 

A scan of the patient’s brain waves (known as an electroencephalography or EEG) can also be taken, although these are not massively useful in the diagnosis of frontotemporal dementia. There has been evidence to show that patients with frontotemporal dementia showed a marked reduction in electrical brain activity when completing tasks that require speed.⁴

Treatment for frontotemporal dementia

There is currently no proven cure for frontotemporal dementia. Clinical trials for several drugs have proven unsuccessful at treating frontotemporal dementia, but trials for novel drugs are still ongoing in an effort to find a successful treatment. 

Non-pharmacological treatment such as physiotherapy, speech therapy, occupational therapy, cognitive behavioural therapy and support from social services is often the go-to choice for treatment with frontotemporal dementia.²

What is the prognosis of frontotemporal dementia?

The risk of mortality is much higher for those with frontotemporal dementia in comparison to Alzheimer’s disease. This may be due to the early onset nature of the disease, which could lead to symptoms not being recognised as that of a form of dementia. This could lead to serious financial or social issues for the patient which puts them at a higher risk. The average survival rate of frontotemporal dementia is 7.5 years.³

Summary

Frontotemporal dementia has three main variants, which can be differentiated via the symptoms patients present with. The specific symptoms of each subtype are key to forming the diagnostic criteria for each subtype. The diagnostic tests remain the same for all subtypes of frontotemporal dementia. These come in the form of a variety of cognitive interviews, lab tests for blood and spinal fluid, various imaging of the brain and sometimes very rarely taking a record of brain activity. Drug treatments have proven unsuccessful, as of yet, and treatment is mostly supportive for this condition. The prognosis for frontotemporal dementia is worse than that of Alzheimer’s due to the earlier onset that is found in frontotemporal dementia compared to that of Alzheimer’s.